Mobile devices having structures that support multi-band communications are known. Many such mobile devices utilize helix, “inverted F” or retractable structures. Helix and retractable antennas are typically installed outside of a mobile device, and inverted F antennas are typically embedded inside of a case or housing of a device. Generally, embedded antennas are preferred over external antennas for mobile communication devices for mechanical and ergonomic reasons. Embedded antennas are protected by the mobile device case or housing and therefore tend to be more durable than external antennas. Although external antennas may physically interfere with the surroundings of a mobile device and make a mobile device difficult to use, particularly in limited-space environments, embedded antennas present fewer such challenges.
In some types of mobile device, however, known embedded structures and design techniques provide relatively poor communication signal radiation and reception, at least in certain operating positions of the mobile devices. One of the biggest challenges for mobile device antenna design is to ensure that the antenna operates effectively in different positions, since antenna position changes as a mobile device is moved. Typical operating positions of a mobile device include, for example, a data input position, in which the mobile device is held in one or both hands such as when a user is entering a telephone number or email message, a voice communication position, in which the mobile device may be held next to a user's head and a speaker and microphone are used to carry on a conversation, and a “set down” position, in which the mobile device is not in use by the user, and is set down on a surface, placed in a holder, or stored in or on some other storage apparatus. In these positions, the user's head, hands and body, the surface, the holder, and the storage apparatus can all block the antenna and degrade its performance. Although the mobile device is not actively being used by the user when in the set down position, the antenna should still operate in this position to at least receive communication signals. Known embedded antennas tend to perform relatively poorly, particularly when a mobile device is in a voice communication position.